1. Field of the Invention
The present invention relates to a DC-to-DC voltage converter, and more particularly, to a DC-to-DC voltage converter employing a capacitive transformer array.
2. Description of the Related Art
It is the objectives of all types of DC-to-DC voltage converter designs to produce output power at the desired voltage level efficiently and to be available in small package sizes. Additional goals for all DC-to-DC voltage converter designs is to also provide fast response times and a wide operational input voltage range. In practice, however, the type of conversion process employed affects all of the goals listed above forcing "trade-offs" between intended application (end use) and the DC-to-DC voltage converter design selected.
Presently there are three basic types of DC-to-DC voltage regulators: Transformer based switching voltage converter-regulators, Linear Voltage regulators, and Switched capacitor voltage regulators. Of these, only the transformer based switching voltage converter designs offer power conversion which also offers the best all around performance. Both the linear regulator and switched capacitor regulator designs implement an attenuation and therefore can not perform power conversion. Hence, the maximum of efficiency of this approach is limited to the ratio of the applied input voltage to the desired output voltage as shown below in equation EQa. This is because with the attenuation approach the input current, I.sub.in, is approximately equal to the output current, I.sub.out. ##EQU1##
The transformer based DC-to-DC voltage converter designs offer the best all around performance in terms of available output power, operational efficiency, and input voltage range. However, these designs generates large amounts of electrical noise, and generally require more board area than either of the linear or switched capacitor regulators. In addition, the response times of the transformer based DC-to-DC voltage converter designs are usually very large. Those applications that does not require any of the major advantages of the transformer based DC-to-DC voltage converter designs usually will implement a solution based on a linear regulator design. Still a smaller number of application will select a switched capacitor based DC-to-DC voltage converter designs due to its size, and when voltage inversion is required. The Table 1 below shows the DC-to-DC voltage converter designs and typical output voltage and power.
TABLE 1 __________________________________________________________________________ DC-to-DC Converter Types Typical Typical Input Output Typical Typical Voltage Voltage Output Operational Convert Type Range Range Power Efficiency __________________________________________________________________________ Switched Capacitor -16 V -12 V to 0.5 W V.sub.out /V.sub.in (3) Regulators (1) +12 V Linear Regulators- V.sub.out + 1.0 V 1.2 V-24 V &lt;1 W-60 W V.sub.out /V.sub.in (3) Series -36 V Linear Regulators- Shunt Transformer Based 5 V-110 V 2.0 V-48 V 2 W- 72%-90% (2) Switchers (1) 1500 W __________________________________________________________________________ (1) Inverted output voltage from positive voltage source (2) Highest efficiency occurs at higher output voltage (3) This is the maximum efficiency possible